Electronic devices vary in structure and design, but invariably involve control of a flow of charged carriers (e.g., electrons or ions) between electrodes (i.e., an anode and a cathode). The flow of charged carriers may be a result of thermionic emission, which is the heat-induced flow of charge carriers from a surface or over a potential-energy barrier, from one of the electrodes. This emission occurs because the thermal energy given to the carrier overcomes the binding potential, also known as work function of the electrode. A classical example of thermionic emission is the emission of electrons from a hot cathode, into a vacuum (also known as the Edison effect) in a vacuum tube. The hot cathode can be a metal filament, a coated metal filament, or a separate structure of metal or carbides or borides of transition metals. The electronic devices may also exploit other physics phenomena (e.g., field electron emission or photoelectric emission) to produce the flow of charged carriers between the anode and the cathode.
The flow of the charged carriers or the emission of charged carriers from the electrode in an electronic device is influenced by proximate structures. For example, a vacuum tube device, in addition to the anode and cathode electrodes, can include one or more active electrodes (or grids) that influence the flow electrons in the device. Vacuum tube devices that include three, four, five and six electrodes, etc. are suggestively called triodes, tetrodes, pentodes, hexodes, etc. The grids in these devices can have different functions. For example, a voltage applied to a control grid that is ordinarily placed between the cathode and the anode of an electron tube serves to vary the flow of current. A screen grid that is ordinarily placed between the control grid and the anode acts as an electrostatic shield to protect the control grid from the influence of the anode when its potential changes. A suppressor grid that is ordinarily interposed between the screen grid and the anode acts as an electrostatic shield to suppress secondary emission from the anode.
Consideration is now being given grid structures and materials in electronic devices. Attention is directed to, but not limited to, micro- and nano-electronic devices in which an inter-electrode dimension may be a microscopic dimension.